Numerous applications are known for semiconductor constructions, and new applications are being developed. Semiconductor constructions can be utilized in, for example, mobile devices, such as, for example, cell phones and other small personal telephones, cameras and personal calendars. It is a continuing goal to make the portable electronic devices smaller and more lightweight, and accordingly it is a continuing goal to reduce the size of semiconductor constructions utilized in the devices while maintaining desired performance characteristics of the constructions.
Typical semiconductor constructions have a die of semiconductor material serving as a base for the constructions. Integrated circuitry is formed to be supported by the die. Such circuitry can comprise portions formed over the die, as well as portions extending within the die (for example, diffusion regions). An exemplary semiconductor die is a silicon-containing material. Such material can comprise, consist essentially of, or consist of silicon lightly doped with appropriate background-type dopant. The die can be referred to as a substrate in some aspects of this disclosure. To aid in interpretation of the claims that follow, the terms “semiconductive substrate” and “semiconductor substrate” are defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above.
One method which has been utilized to reduce the size of semiconductor constructions is to reduce the thicknesses of the semiconductor dies utilized in such constructions. Each die utilized in a semiconductor construction will typically have a front surface configured for supporting integrated circuitry thereon, and a back surface in opposing relation to the front surface. The die are thinned by removing material from the back surface until a desired thickness of the resulting die is achieved. Such removal can be accomplished by first subjecting the die to a coarse roughening to remove the majority of the material, and subsequently removing the remainder of material with a chemical-mechanical polish to form a smooth surface over the remaining back of the thinned die.
An exemplary thinned semiconductor die 10 is shown in FIG. 1. Such die comprises a front surface 12 and a back surface 14 in opposing relation to the front surface. The front surface would generally support integrated circuitry (not shown). Sidewall surfaces 16 extend from the front surface to the back surface. A thickness of the die (i.e., a length of sidewall surfaces 16) is typically less than 400 microns, frequently less than 100 microns, less than 50 microns, less than 20 microns, or even less than or equal to about 15 microns. Although the die of FIG. 1 is shown flat, it is to be understood that the die can have a more curved configuration, such as, for example, the configuration shown in FIG. 2. Such curved configuration results from tensile and/or compressive forces exerted on and/or within the die. Typically, the die will have a curved configuration. Such is well known to persons of ordinary skill in the art, and integrated circuitry is frequently fabricated to have optimal performance when the die is within a particular curved configuration. If the die is within tolerances of the desired curvature, the die is considered to be within the “sweet spot” for device performance.
The present invention is motivated, in part, to address various problems associated with thin dies. For instance, it is found that performance characteristics of thin dies frequently do not fall within desired tolerances, and accordingly the rejection rates of the dies can be unacceptably high. The poor performance characteristics of the dies can result from the dies having the wrong curvature to fall within the “sweet spot”, or can result from other causes. It is desired to improve thin die constructions in order to reduce rejection rates. Although the invention was motivated by particular problems, it is to be understood that the invention is not so limited. Rather, the invention is only limited by the accompanying claims as literally worded, and in accordance with the doctrine of equivalents.